For an extracorporeal blood treatment with a device such as a dialysis machine, blood of a patient is conveyed through an extracorporeal blood circulation for instance in the course of a hemodialysis, hemofiltration or hemodiafiltration. In order to gain access to the intracorporeal blood vessel system of the patient, arteriovenous fistulas, shunts or also vessel implants are used as a rule. The connection between the extracorporeal blood circulation and the patient is usually effected with catheters or cannulas or needles, e.g. dialysis cannulas or needles, which serve for puncturing a fistula, shunt or vessel implant, for example.
In the context of such a blood treatment, malfunctions may occur in the extracorporeal blood circulation, which are shortly termed as FEB. One example of an FEB is a needle disconnection. In such a situation, the access to the blood circulation of the patient is defective, for instance if a needle or cannula gets out of place and the extracorporeal circulation is not properly connected to the intracorporeal blood circulation or patient's blood circulation any more. This may be problematic in particular in the event of a disconnection of a venous access to the patient's blood circulation. If such incident is not identified in due time, blood is still taken from the patient via an arterial access, but is not conveyed back to the patient (or only in an unsufficient amount) after the extracorporeal blood treatment. With the usual blood flow rates of approximately 300 to 400 ml/min, a life-threatening situation may arise within few minutes.
The identification of malfunctions in the extracorporeal blood circulation, in particular the recognition of a venous needle disconnection, is a severe problem in medical treatments using an extracorporeal blood circulation such as the hemodialysis. In the USA alone, approximately one hundred people die each year from the consequences of a venous needle disconnection (Hurst, Jane, “Venous Needle dislodgement—A Universal Concern.” European Nephrology).